Process for puffing tobacco

ABSTRACT

Tobacco having at least 6 percent moisture is impregnated with ammonia and carbon dioxide to introduce into the tobacco preferably from about 3 percent to about 6 percent by weight of ammonia and from about 2 percent to about 8 percent of carbon dioxide based on the weight of the tobacco. The tobacco is thereafter heated at a temperature of from 250* F to about 700*F for a time sufficient to puff the tobacco.

United States Patent. [191 Armstrong et a1.

[ PROCESS FOR PUFFING TOBACCO [75] Inventors: Robert G. Armstrong;Edward J.

Deszyck; John W. Madures, all of Richmond, Va.; Robert H. Young, EastBrunswick, NJ.

[73] Assignee: Philip Morris Incorporated, New

York, NY.

22 Filed: Aug. 31, 1970 21 App1. No.: 68,532

[ Nov. 13, 1973 246,975 9/1881 Philips 131/142 A 1,927,984 9/1933Krensky et al. 131/17 B 1,789,435 1/1931 Hawkins 131/140 P 3,575,1784/1971 Stewart 131/140 P 3,524,451 8/1970 Fredrickson 131/140 P1,996,797 4/1935 Dreyfus 131/140 P 2,085,052 6/1937 Taylor 131/140 PPrimary ExaminerMelvin D. Rein Attorney-Watson, Leavenworth and Kelton[5 7] ABSTRACT Tobacco having at least 6 percent moisture is impregnatedwith ammonia and carbon dioxide to introduce into the tobacco preferablyfrom about 3 percent to about 6 percent by weight of ammonia and fromabout 2 percent to about 8 percent of carbon dioxide based on the weightof the tobacco. The tobacco is thereafter heated at a temperature offrom 250 F to about 700F for a time sufficient to puff the tobacco.

9 Claims, No Drawings PROCESS FOR PUFFING TOBACCO BACKGROUND OF THEINVENTION The art has recognized the desirability of increasing the bulkor volume of tobacco for various reasons. An early purpose was to makeup the loss of weight caused by the curing process. A further reason forexpanding tobacco was to improve the smoking characteristics of tobaccostems. Another purpose was to increase the filling power so that asmaller amount of tobacco would be needed to produce a firm cigaretterod or the like, which would produce lower tar and nicotine than acomparable product made of unexpanded tobacco.

A patent to Hawkins, U.S. Pat. No. 1,789,435 granted in 1931 describes amethod and apparatus for expanding the volume of tobacco in order tomake up the loss of weight caused in curing tobacco leaf. To accomplishthis object the cured and conditioned tobacco is subjected to air,carbon dioxide or steam under pressure and then on release of pressurethe tobacco tends to expand. The patent states the volume of the tobaccois increased to the extent of about 515 percent.

, A series of patents to Burde, granted in 1968, specifically U.S. Pat.No. 3,409,022, 3,409,023, 3,409,027 and 3,409,028, describe proceduresfor enhancing the utility of tobacco stems for use in smoking productsby subjecting the stems to a puffing operation utilizing various typesof heat treatment or microwave energy.

A patent to Hind granted in 1969, U.S. Pat. No. 3,425,425 also relatesto the use of carbohydrates to improve the puffing of tobacco stems. Inthe process, tobacco stems are soaked in an aqueous solution ofcarbohydrates and then heated to puff the stems. The carbohydratesolution may also contain organic acids and- /or certain salts which areused to improve the flavor and smoking qualities of the stems.

A publication in the Tobacco Reporter of Nov. 1969 by P.S. Meyerdescribes and summarizes tobacco puffing or expansion procedures orinvestigations for expanding and manipulating tobacco for purposes ofreducing costs and also as the means for reducing the tar content byreduction in the delivery of smoke. Mention is made in this publicationof puffing tobacco by differentprocedures including the use ofhalogenated hydrocarbons, low pressure or vacuum operation, or highpressure steam treatment that causes leaf expansion from inside the cellwhen outside pressure is suddenly released. Mention is also made in thispublication of freeze-drying tobacco which apparently causes an increasein volume.

Thus far, no completely satisfactory process has been found. Thedifficulty with the various earlier suggestions for expanding tobacco isthat, in many cases, the volume is only slightly or at best onlymoderately increased, noting for example, the percent expansion as themaximum achieved by Hawkins. On the other hand, while a substantialvolume increase may be achieved by freeze-drying, this type of operationhas the disadvantages of requiring elaborate and expensive equipment andvery substantial operating costs. With respect to the teaching of usingheat energy, infrared or radiant microwave energy to expand tobaccostems, the difficulty is that while stems respond to these heatingprocedures, tobacco leaf does not respond effectively to this type ofprocess.

The use of special expanding agents, for example, halogenatedhydrocarbons, such as are mentioned in the Meyer, publication forexpanding tobacco, is also not completely satisfactory because thesesubstances are generally relatively expensive and because a hightemperature is generally required to volatilize or remove the substancesafter the tobacco has been expanded. The introduction, in considerableconcentration, of materials which are foreign to tobacco presents theproblem of removing the expansion agent after the treatment has beencompleted in order to avoid affecting aroma and other properties of thesmoke due to extraneous substances used or developed from the combustionof the treated tobacco.

The present invention relates broadly to the puffing of tobacco with arelatively inexpensive, low combustibility, volatile and nontoxic agentand more particularly to the production of a puffed tobacco product ofsubstantially reduced density produced by impregnating tobacco withammonia and carbon dioxide and then subjecting the impregnated tobaccoto expansion conditions such as heat, or reduced pressure or both, or toother known radiant energy conditions as previously mentioned.

To carry out the process of the invention, one may treat either wholecured tobacco leaf, tobacco in cut or chopped form, or selected parts oftobacco such as tobacco stems or reconstituted tobacco. In comminutedform, the tobacco to be impregnated may have a particle size of about 20to 5 mesh, but preferably not less than about 30 mesh. The materialtreated'may be in rel atively dry form, or may contain the naturalmoisture content of tobacco. Preferably the tobacco should have at leastabout 6 percent moisture but less than 35 percent moisture. The reasonfor the upper limit will be provided in the further description of theinvention.

The essential feature of the invention process is the expansion orpuffing of the tobacco utilizing ammonia and CO as the primary expandingagents. It is believed that the ammonia under .the conditions ofoperation and possibly in the presence of some moisture, causes theexpansion of the tobacco to a greater and less reversible extent thancan be obtained with various other expanding agents.

The pretreatment of tobacco may be with liquid or gaseous ammonia orwith ammonium hydroxide to permit absorption of ammonia into the tobaccocellular structure. A preferred method is to introduce both ammonia andcarbon dioxide into the tobacco or by contacting tobacco'with eitherammonium carbonate or ammonium bicarbonate applied directly, or formedinsi'tu by the reaction of ammonia with carbon dioxide and moisture inthe tobacco. In any of the procedures indicated, substantial expansiontakes place on heating the impregnated tobacco either by means of theammonia alone or the combined effects of both ammonia and carbon dioxidewithin the tobacco structure.

The treatment of tobacco with ammonia may be by direct contact withliquid ammonia, solutions of ammonia, ammonia vapor or by substancescapable of evolving ammonia such as by incorporating ammonium carbonateor bicarbonate in the tobacco to be treated. Sufficient time is providedto result in impregnating at least 1 percent by weight of ammonia or itsequivalent into the tobacco cell structure for acceptable expansion,with 2.5 percent to 8 percent by weight absorbed being preferred.

dure is to use liquid ammonia applied in a form of a spray, followed bya period of stabilization or equilibration of a'few minutes to 24 hoursto effect the desired absorption and retention of the agent in thetobacco. Substantial addition of ammonia to the tobacco may thus bereached, amounting to as much as 100 percent by weight. However, athorough spraying for five minutes is satisfactory requiring no furtherstanding, with about 50 percent absorption being achieved.

Another method in the use of liquid ammonia is to dip the tobacco intoliquid ammonia for a period of one to two minutes followed by drainingand standing or re taining the treated tobacco in a closed vessel up totwo to four hours. This will result in about eight to about 12 percentabsorption. Satisfactory absorption may be achieved by dipping thetobacco into liquid ammonia for about five minutes and merely drainingthe tobacco on withdrawal. By this procedure about 50 percent of ammoniais absorbed. Concentrated ammonium hydroxide may alternatively be usedas a substitute for liquid ammonia, the tobacco being held therein forabout one to two minutes.

Ammonia vapor may also be used, for example, by exposing the tobacco toammonia vapors from an aqueous solution of ammonia (ammonium hydroxide)for a period of one hour to one week but preferably from about four to24 hours which results in an ammonia intake of from 1 percent to about12 percent by weight with additional intake of some moisture. Ingeneral, where tobacco is exposed to ammonia long enough to absorb 2percent or more, the impregnated tobacco should not be exposed to theair for more than a few minutes before puffing, so that undesirabledarkening is avoided.

By following the above described ammonia vapor procedure for ammoniaabsorption, the tobacco can be impregnated with from 1 percent to ashigh as 50 percent by weight ammonia depending on the partial pressureof the ammonia vapor over the aqueous ammonia. As indicated previously,about 2.5 to 8 percent ammonia impregnation is preferred.

While ammonia by itself is a satisfactory puffing agent, it has beenfound that excellent results are achieved by combining the effects ofammonia and carbon dioxide puffing by introducing both of theseexpansion agents into the tobacco. To obtain the combined effects, apreferred procedure is to expose tobacco to ammonia vapors or gas, thenCO gas or the reverse, and, if desired, adding powdered carbon dioxide,allowing the ammonia and carbon dioxide sufficient time to be absorbed.About 10 minutes to an hour of exposure to the ammonia vapor followed bythe same length of time for CO with cooling by the use of a water jacketor the like will yield a satisfactory amount of impregnation. Theabsorption may be improved if the impregnation vessel is first evacuatedto a low initial pressure up to 26 in. of mercury absolute. Th amountsand rates of absorption are determined by the rates at which heat can bedissipated from the mass of tobacco undergoing treatment and the finaltemperature attained since there is an exothermic heat of solution andreaction of the ammonia, carbon dioxide and the moisture in the tobacco.It is therefore best to keep the temperature of the tobacco undergoingabsorption at a reasonably low point, below about 100F. and preferablyin the neighborhood of about 75F. by cooling, to achieve satisfactoryabsorption and formation of ammonium carbonates in the tobacco.

An alternative method employs ammonium carbonate or ammonium bicarbonatefor supplying both ammonia and carbon dioxide as expansion agents fortobacco. One procedure for obtaining impregnation of these compounds isto subject the tobacco in an enclosed zone from 24 to 96 hours to theammonia and carbon dioxide gas that is given off or released from theammonium carbonates, permitting these gases to be absorbed and to reactwith the moisture present to form ammonium carbonates. Penetration ofthe gases and formation of ammonium carbonates in the tobacco isexpedited if the tobacco impregnation chamber is first evacuated.Pressures ranging up to 26 in. of Hg absolute may be used. Absorption isenhanced by cooling the contents to hold the temperature of the tobaccobelow about 100F. Following the impregnation, completed when thetemperature is in the neighborhood of about F., the tobacco is held forabout 15 minutes to one hour before the final puffing step.

Still another procedure is to utilize ammonium carbonate or ammoniumbicarbonate in the form of a dust applied to tobacco leaf in an amountof about 1-25 percent by weight of the tobacco. The treated tobacco isthen held for about 18 to 96 hours but preferably about 24 hours issufficient for equilibration and retention of about four to eightpercent of the carbonates within the tobacco structure.

A still further method for impregnating tobacco with ammonium carbonateor bicarbonate is to contact the tobacco with these salts suspended orpartially dissolved in a suitable liquid medium for about 1 to 48 hours,permitting the carbonates to be absorbed along with some absorption ofthe liquid medium itself. Examples of liquid carriers or solvents thatmay be used are methylene chloride or highly concentrated methanol orethanol aqueous solutions comprising about 75 to percent alcohol. Theliquid solvent or carrier may be removed in good measure by exposing thetobacco to a flow of inert gas or air before puffing.

In the impregnation of tobacco with carbonates, whether by contactingthe tobacco with ammonia and carbon dioxide, or when these gases areproduced from impregnation with ammonium carbonate or bicarbonate, goodsubsequent expansion to densities of about 0.25 has been found when theindividual levels of ammonia and CO in the penetrated tobacco is intherange of about 3 to 6 percent by weight of ammonia and 2 to 8 percent byweight of carbon dioxide.

An important advantage in the use of ammonium carbonate or bicarbonateis the fact that these compounds easily decompose at temperatures quitesubstantially below the charring temperature of tobacco. A still furtheradvantage is that the treated tobacco need not be expanded immediatelybut may be stored or handled for short periods in air without loss ofpuffing capacity.

Following the impregnation of the tobacco by the various means describedabove, the impregnated tobacco is then exposed to expansion conditionsby subjecting the treated product to heat or the equivalent, or toreduced pressure or a combination of these effects. This may comprisethe use of hot surfaces, or a stream of hot air, a mixture of gas andsteam, or exposure to radiant energy such as radiant microwave energy orinfrared radiation. Another method for causing expansion after theammonia treating step is to subject the treated leaf toa sudden decreasein pressure as for example in guns such as are commonly used for puffingcereals. A convenient means of expanding treated tobacco is to entrainit in a stream of heated gas, such as superheated steam, which serves tocarry away the expelled ammonia which may subsequently be recovered forreuse.

As is well known in processing of any organic matter, overheating cancause damage, first to color, such as undue darkening, and finally, tothe extent of charring. The necessary and sufficient temperature andexposure time for puffing without such damage is a function of these twovariables as well as the state of subdivision of the tobacco. Thus, toavoid undesirable damage in the heating step, the impregnated tobacco,at heating temperatures in the neighborhood of 700F., should not beexposed to such temperatures for longer than the time it takes for thetobacco particles to attain a temperature of about 285F., which isnormally about 0.1 seconds.

One method for causing the expansion of the tobacco cells is to use theradiation methods described in either U.S. Pat. No. 3,409,022 or No.3,409,027. Another method involves the use of a heat gun such as theDayton heat gun or the equivalent, operating at an exit air temperatureof 375-650F. for a period of about 0.2 seconds to four minutes, theshorter times of course being given for the higher temperatures. In thisoperation, the tobacco never attains a temperature above about 285F.,being cooled by the rapid evolution of gases.

Another system, usually preferred, is to' use a dispersion dryer, forexample, one that is supplied either with steam alone or in combinationwith air. An example of such a dryer is a Proctor & Schwartz PBdispersion dryer. The temperature in the dryer may range from about250-700F. with contact time in the dryer of about four minutes at thelowest temperature to about 0.1 to 0.2 seconds at the highesttemperature. In general, a 0.1 to 0.2 second contact time is utilizedwhen the hot gas temperature is 500-600F. or somewhat higher. As statedbefore, other known types of heating means may be used as long as theyare capable of causing the impregnated tobacco to puff without excessivedarkening. It should be noted, that where a high percentage of oxygen ispresent in the hot gases, it will contribute to darkening, so that if ahot-steam mixture is employed, a high proportion (e.g., over 80 percentby volume) of steam is preferred.

When tobacco with very high moisture content is treated with ammonia andpuffed by heat, or ammoniatreated tobacco is heavily moisturized beforeheat puffing, the product may become unnecessarily darkened. It has notbeen shown that smoke flavor or other properties are particularlyaffected, but where light color is desired excess moisture should beavoided. The moisture level that has been observed to cause darkening isin the neighborhood of about 35 percent or higher. The moisture contentin the tobacco prior to the above described treatment should be in therange of about 3 percent to 25 percent and preferably from about 5percent to about percent to avoid undesirable darkening effects.

A measurement of the expansion effect produced in the tobacco by theabove procedures may be carried out by determining the percentage of theproduct that floats on a specific low density liquid such as acetone,

alcohol, petroleum ether or hexane, or by measuring the density of theproduct by a simple application of the weight in air vs weight in liquidmethod, with acetone as the immersion liquid. A perforated metal case(conveniently a tea ball) holds the sample (3-5g.). The weight in liquidis recorded when the balance has come to rest (60 to seconds). The onlyprecaution is to see that all bubbles have been released by tapping thecase, if necessary, during both the tare and sample weighings.

As described herein, a density of the final puffed tobacco product inthe range of 0.25 to 0.60g./cc. is preferred. i

The following examples will serve to illustrate the techniques ingreater detail. It should be noted that percentages as given in theexamples are on a weight basis, unless otherwise indicated.

EXAMPLE 1 Bright tobacco in the form of cut filler and having a moisturecontent close to 12 percent is sprayed with a mist of liquid ammonia fora period of five minutes. The flow rate of gas through a Proctor &Schwarz PB. dispersion dryer (attached at outlet to a cyclone separator)is set at 2200 ft/min., at a superheated steam/air mixture in a ratio(volume) of about 90/10. Inlet temperature is 550F. The treated filleris fed into the system and the estimated exposure time is two seconds.The product is well puffed and has color equivalent to that beforetreatment or slightly lighter.

EXAMPLE 2 EXAMPLE 3 Cut filler weighing 15 g. was sprayed in apolyethylene bag with 10 ml. of aqueous ammonium hydroxide (30 percentN11 and left in the closed bag several days. With the dispersion dryerset at 2200 ft/min. su- 4 perheated steam/air (5:1 approx. volume ratio)flow, 525F and 420F at inlet and outlet, respectively, the filler wasgiven two passes through the system for an estimated four-secondexposure (after one pass it was still damp). The product was puffed andabout percent floated on absolute ethanol.

EXAMPLE 4 Cut filler was exposed over aqueous ammonium hydroxideover-night to impregnate it with ammonia. The filler was then exposed toCO gas and finally it was mixed with powdered solid carbon dioxide toallow the ammonia, carbon dioxide, and moisture to react. The filler waspassed through the dispersion dryer (2000 ft/min. steam/air, approx.5:1, 550F and 450F at inlet and outlet). The filler was puffed and 95percent floated on absolute ethanol.

EXAMPLE Burley filler (moisture 12-15 percent) was sprayed with liquidammonia for varying lengths of time, then exposed in a rotating wirecage to air from a Dayton heat gun at approximately 400F for onerninute, followed by one minute of air with the heat off. The degree ofpuffing was noted by the fraction of filler which floated on varioussolvents: ethanol, d. 0.794; petroleum ether, d. 0.733; hexane, d.0.687. Results are shown in Table I.

Table I Puffing of Burley Filler (Con- NI-l, spray, min. 1 3 5 0 trol)*Floating on absolute ethanol 100 100 100 Floating on petroleum ether 50100 100 5 Floating on liquid hexane 25 90 100 5 *l-leating just sec. toavoid charting.

Bright filler with five minute spray also showed 100 percent floating.Microscopic examination of sectioned particles led to estimate of atleast 100 percent expansion in cross-section thickness.

EXAMPLE 6 Cut Burley filler at varying moisture levels was sprayed withanhydrous liquid ammonia for five minutes and treated with air at 400Ffor 70 seconds from the Dayton heat gun. Results are shown in Table II.Acetone has (1. 0.782.

TABLE II Puffing of Burley Filler Moisture 2.8 12.0 17.8 20.8 Floatingon acetone 0 100 100 100 Floating on petroleum ether 0 70 100 100Floating on liquid hexane 0 70 100 100 In another test, appreciablepuffing occurred at 5.5 percent initial moisture, and puffing at 19.4and 25.3 percent initial moisture was approximately equal.

EXAMPLE 7 A 4.8 liter glass resin-flask was fitted with a chromelalumeltemperature probe connected to a recorder, and with connections tosources of vacuum, gaseous C0,, gaseous ammonia and a vacuum gage. 40grams of bright tobacco was placed in the container. A vacuum of inches(of mercury) was drawn or about 1/3 of an atmosphere absolute pressureand CO was introduced to a vacuum of 10 inches. Then ammonia wasintroduced to a vacuum of two inches. During the next 20 minutes,ammonium bicarbonate deposited in the tobacco causing a temperature riseof 11.7C. After two hours, the temperature had returned to ambient (26C)and the pressure had returned to 10 inches. The container was thenfilled with more C0, (to ambient pressure) and almost no furthertemperature change was observed.

Calculations, based on the amounts of CO and ammonia added, indicatedthat nearly percent excess CO, appeared to have been present initially.Converting the temperature rise to calories of heat evolved, it wascalculated that about 60 percent of the ammonia present had reacted onthe tobacco to the equivalent of ammonium bicarbonate. The sample wassubsequently puffed as in Example 4 at 5 00F and showed percent floaterson petroleum ether.

EXAMPLE 8 One hundred and ninety grams of flue cured tobacco at 7.7percent moisture was stored for 72 hours with 68 grams of commercialammonium carbonate at a partial pressure of 44 mm. The pressure rose toan equilibrium of 180 mm after a few hours. About nine grams of thecarbonate sublimed, and a total of nearly six grams of ammonia and COwas found on the tobacco by analy- SlS.

The treated tobacco from the above experiments was expanded in thedispersion dryer at 400 and 550F with 1.8 percent NH and 1.2% CO,produced in the tobacco, expansion densities found were 0.60 at 400F and0.41 at 550F.

EXAMPLE 9 Cut bright leaf filler was dipped in methylene chloridesaturated with ammonium carbonate. It was exposed for two days to theair. When this filler was placed on a hot plate, it puffed with someaudible popping but without the more violent and irregular p0p pingobserved with methylene chloride. Most of the solvent had apparentlybeen lost before the pufiing.

EXAMPLE 10 In equipment like that used in Example 7, 40 grams of E-7bright tobacco filler was evacuated and exposed to ammonia vapor atatmospheric pressure. After about 30 minutes the tobacco was removed andsubjected to steam/air (/10) in the dispersion dryer at an inlettemperature of 500F. approx. Density was found to be 0.27g./cc. ascompared with 1.14g./cc. for the filler before treatment.

EXAMPLE 1 1 Fifty pounds of filler-cut flue-cured tobacco at 11 percent(dry basis) moisture was charged to a large tumbler cooled by water at42F. The tumbler was set in motion at 6 RPM and evacuated to about oneinch Hg (absolute pressure). Then, four pounds of liquid ammonia wasinjected in a period of 10 mins., followed by six pounds of CO (gas)during a period of 30 mins. The use of liquid rather than gaseousammonia greatly reduced the amount of heat evolved when tobacco isammoniated. The residual vacuum was then discharged by admitting air.The impregnated tobacco was analyzed and contained 4.4% NH 5.3% CO and18.6 percent (dry basis) total oven volatiles. It was injected into ahigh velocity turbulent stream of combustion gases and steam at 500F.and yielded a low density (0.28), (The density was measured by anacetone displacement method.) light yellow-colored, expanded product.

When equilibrated after treating in a fine water spray to 13 percentmoisture, this material showed a filling index about twice as great asuntreated tobacco at a similar moisture content.

It should be noted that ammonia is naturally present in tobacco butobviously at levels substantially below that needed for significantexpansion. The fact that ammonia is a natural constituent of tobacco isa material advantage in carrying out the puffing process of theinvention as described here. Thus, it is not necessary to remove everytrace of the expansion agent before the product is incorporated intosmoking articles as is clearly necessary when using such foreign andextraneous materials as hydrocarbons or halogenated compounds forexpansion purposes. Ammonia. also has the advantage of being relativelymuch less hazardous in forming explosive mixtures with air than would beencountered if one used some of the organic liquids that have beenpreviously suggested.

Ammonia is especially efficacious in causing puffing of tobacco partsbecause first it readily penetrates the cell walls and second at leastin the presence of moisture is believed to have a softening effect onthe cell structure which facilitates the puffing. Moreover, its lowboiling temperature (vapor pressure) makes possi- Me the use ofrelatively low puffing temperatures. A further advantage is therelatively low cost of ammonia which means that losses due to incompleterecovery are of no great concern.

An important advantage in the use of ammonium carbonate or bicarbonateis that these compounds not only have negligable explosion hazard ascompared to other substances but also have the advantage of producingammonia and carbon dioxide at relatively low temperatures whereasexcessive darkening and charting temperatures could be incurred withother substances capable of furnishing a gaseous puffing agent but onlyat a relatively high decomposition temperature. Thus, tobacco puffedwith ammonia that is either absorbed or produced in situ shows little orno darkening in the absence of an excess amount of moisture. The latter,of course, can be prevented by avoiding the deliberate addition of wateras is sometimes believed necessary in prior processes.

The invention claimed is:

l. The process of puffing tobacco comprising the steps of contactingtobacco containing at least about 6 percent moisture by weight in animpregnation zone with ammonia and with carbon dioxide at or aboveatmospheric pressure to introduce into the tobacco from about 3 percentto about 6 percent by weight of ammonia based on the weight pressurebelow atmosphere of about 26 inches mercury absolute or less to absorbcarbon dioxide into the tobacco and then puffing the impregnated tobaccoby heating to 250 to about 700F for a time sufficient to puff thetobacco.

2. The process of claim 1, wherein the ammonia is separately added tothe tobacco and the carbon dioxide is thereafter separately added to thetobacco, both additions being prior to the heating step.

3. The process of claim 1, wherein carbon dioxide is separately added tothe tobacco and the ammonia is thereafter separately added to thetobacco, both additions being prior to the heating step.

4. The process of claim 1, wherein the ammonia and carbon dioxide areadded simultaneously to the tobacco prior to the heating step.

5. The process of claim 1, wherein said heating is effected by means ofa member selected from the group consisting of steam, hot air andmixtures thereof.

6. The process of claim 5, wherein said heating is conducted at atemperature of from about 375 to about 650F. for a period of time offrom about 0.1 second to about four minutes.

7. The process of puffing tobacco comprising the steps of contactingtobacco containing at least about 6 percent moisture in an impregnationzone with from about 1 to 12 percent by weight of ammonia at a lowpressure below atmospheric to absorb ammonia into the tobacco, thencontacting the tobacco with carbon dioxide at a pressure belowatmospheric to absorb carbon dioxide into the tobacco, the temperatureof contact being significantly below 100, and then puffing theimpregnated tobacco by heating to a temperature in the range of 250700F.

8. The process of claim 7, wherein the ammonia impregnation is carriedout with liquid ammonia.

9. The process of claim 7, wherein the moisture content of the tobaccoprior to ammoniacal treating is in the range of about 5 to about 20percent by weight.

2. The process of claim 1, wherein the ammonia is separately added tothe tobacco and the carbon dioxide is thereafter separately added to thetobacco, both additions being prior to the heating step.
 3. The processof claim 1, wherein carbon dioxide is separately added to the tobaccoand the ammonia is thereafter separately added to the tobacco, bothadditions being prior to the heating step.
 4. The process of claim 1,wherein the ammonia and carbon dioxide are added simultaneously to thetobacco prior to the heating step.
 5. The process of claim 1, whereinsaid heating is effected by means of a member selected from the groupconsisting of steam, hot air and mixtures thereof.
 6. The process ofclaim 5, wherein said heating is conducted at a temperature of fromabout 375* to about 650*F. for a period of time of from about 0.1 secondto about four minutes.
 7. The process of puffing tobacco comprising thesteps of contacting tobacco containing at least about 6 percent moisturein an impregnation zone with from about 1 to 12 percent by weight ofammonia at a low pressure below atmospheric to absorb ammonia into thetobacco, then contacting the tobacco with carbon dioxide at a pressurebelow atmospheric to absorb carbon dioxide into the tobacco, thetemperature of contact being significantly below 100, and then puffingthe impregnated tobacco by heating to a temperature in the range of 250*-700*F.
 8. The process of claim 7, wherein the ammonia impregnation iscarried out with liquid ammonia.
 9. The process of claim 7, wherein themoisture content of the tobacco prior to ammoniacal treating is in therange of about 5 to about 20 percent by weight.